1. Field of the Invention
The present invention relates to a shutter device. More specifically, it is mounted on the process cartridge for protecting a photosensitive rotary drum.
2. The Prior Art
There have been known various image forming apparatuses, such as a photographic copying machine, an electro-photographic printer (for example, a LED printer or a laser beam printer), and an electro-photographic facsimile machine, an electro-photographic word processor, and the like.
In the drawing, FIG. 1, which provides a process cartridge 1a being removably installed at a predetermined location in the main assembly of the electro-photographic printer. The process cartridge 1a comprises four devices: a photosensitive rotary drum 2a as an image bearing member, a rotary charge roller 3a as a charging member for charging the photosensitive rotary drum 2a, a developing device 4a, and a cleaning device 5a, which are integrally disposed in the cartridge shell, holding a predetermined positional relationship among them.
A referential numeral 20a designates a drum cover. It is attached to the underside of the process cartridge 1a and covers a bottom of the photosensitive rotary drum 2a, so as to protect the photosensitive rotary drum 2a when the process cartridge 1a is out of the main assembly of the printer. It is moved to a position illustrated in FIG. 1 to expose the bottom of the photosensitive rotary drum 2a as the process cartridge 1a is installed into the main assembly of the printer. When the process cartridge 1a is at the predetermined location in the main assembly of the printer, the exposed bottom portion of the photosensitive rotary drum 2a is placed in contact with a transfer roller 10a, as a transferring means, on the printer main assembly side, with a predetermined contact pressure, and form a transfer nip for conveying paper.
It is an object of the present invention to provide a shutter device, which has a better protection for a photosensitive rotary drum, and in the meanwhile, can be as a switch of an exposure window of the process cartridge.
In accordance with one aspect of the present invention, which provides a shutter device for protecting a photosensitive rotary drum, comprising a drum cover, a torsion spring, a press button and a compression spring. The drum cover has a fixed end pivotally connected to a predetermined location of a process cartridge, a free end shielded on an exposed portion of the drum and an inside surface formed with a hook, and the torsion spring is arranged on the fixed end of the drum cover. The press button is received in a room of a side of the process cartridge, and the compression spring is positioned between a protruded rod formed inside the press button and a sleeve disposed on the room of the process cartridge.